Semiconductors, or computer chips, are found in virtually every electrical product manufactured today. Chips are used not only in very sophisticated industrial and commercial electronic equipment, but also in many household and consumer items such as televisions, clothes washers and dryers, radios, and telephones. As products become smaller but more functional, there is a need to include more chips in the smaller products to perform the functionality. The reduction in size of cellular telephones is one example of how more and more capabilities are incorporated into smaller and smaller electronic products.
Ball Grid Array (hereinafter referred to as BGA) packaging is widely applied to package the integrated circuits of chip sets or graphic chips, etc. Conventionally, the BGA packaging has tin balls provided on the bottom surface of a substrate and arranged in a form of an array. The balls serve as the leads or pins (conductive media) between a chip (or IC) and a circuit board, replacing the conventional lead frames. The BGA packaging can provide not only more pins but also more space between every two adjacent pins than that of conventional packaging, under the same size of substrate. In addition, BGA packaging provides superior heat dissipation and electrical conductivity by providing shorter conducting paths between the chip and the circuit board.
According to the raw material of the substrate, BGA substrates are divided into three categories: Plastic BGA (PBGA), Metal BGA (MBGA), and Tape BGA (TBGA). The PBGA substrate is made of organic materials such as compounds of BT resin and glass fiber. It is the most popular BGA substrate in the packaging industry.
To meet the need for shrinking package sizes and growing lead counts, flip chip and ball grid array (BGA) technologies have become increasingly popular. Flip chip relates to the attachment of an integrated circuit to a substrate while BGA relates to the attachment of a substrate to a printed circuit board or the like. Flip chip BGA packages (FCBGA), which combine the two technologies, are relatively small and have relatively high lead counts.
One conventional method of creating components of such wafer level package structures is shown in FIG. 1. A plurality of input/output 202 are disposed on a semiconductor substrate 201, and are used to transmit input or output signals. The input/output 202 are usually made of metal, such as gold (Au), aluminum (Al), or copper (Cu). The semiconductor substrate 201 and the input/output 202 are both covered by a passivation layer 203. The passivation layer 203 is usually made of oxide, (such as silicon dioxide (SiO.sub.2)), nitride (such as silicon nitride (Si.sub.3N.sub.4)), or other organic compounds (such as polyimide (PI)). The passivation layer 203 covers the semiconductor structure so as to protect circuits on the semiconductor structure 201.
A series of metal protection layers 204a, 204b, and 205 are used to protect the passivation layer 203 from damage. An under bump metallurgy layer (UBM layer) 206 is deposited on the protection layer 205. The under bump metallurgy layer 206 is usually made of copper (Cu), CuNi, gold (Au), or alloy, and is used as an adhesion layer for the metal solder bump 207. The metal solder bump 207 is located over the under bump metallurgy layer 206, and are usually made of conductive materials which can be used in electroplating technology, such as Sn/Pb alloy, copper (Cu), gold (Au), nickel (Ni), or indium (In).
In the manufacturing process involving high-topography, electroplated copper (Cu) pads, passivation material such as passivation layer 203 tends to crack. Hence, the prior art use of protection layers 204a, 204b, and 205 is implemented as a possible solution to protect the passivation layer 203. In addition, polyimide (PI)/copper (Cu) interfaces typically located at the bottom of a via are attacked during the solder bumping process. Such protective measures as found in the prior art, however, are expensive and involve extra manufacturing steps which create additional manufacturing time and complexity in the manufacturing process.